Circuit interrupter



July "20,1926.

G. A. BURNHAM CIRCUIT INTERRUPTER Filed March 25', 1922 null I In veniof. 7 v 9- Q .5, x

Patented July 20, 1926.

UNITED STATES v 1,593,206 PATENT OFFICE.

GEORGE A. BUBNHAM, OF SAUGUS, MASSACHUSETTS, ASSIGNOB, BY MESNE ASSIGN- MENTB, TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF BOSTON, MASSACHUSETTS, A. CORPORATION OF MASSACHUSETTS.

CIRCUIT INTERRUPTER.

Application filed March 25, 1922. Serial No. 548,647.

This invention relates to circuit interrupters and has particular reference to oil immersed electric switches.

When an oil immersed electric switch is opened under substantialrload, gas and vapor may be generated from the oil in the switch and commingle with the air in the expansion space above theswitch to form a combustible mixture. If the switch is reclosed and, while the combustible mixture still exists abovethe oil in theswitch, the

switch is again opened under severe current conditions, the combustible mixture may be ignited and an explosion may occur which may do damage.

If, however, the combustible mixture is removed, or the switch is ventilated, before it is again opened under load, the switch may thenfbe opened without damage.

' An object of this invention is the provision of means to control the time eriod between succes'sive openings of t e switch whereby to permit the switch to be reconditioned for eflicient operation at it's rated capacity for each opening.

In oarryin out this object of the invention, I'provi e means to prevent the reclosing of the switch after it is opened until a suitable and predetermined time period has elapsed. Said governing means may be arranged to be energized from the tripping circuit of the switch to control-the closin circuit of the switch and remove the contro of the closing circuit from an operator, or from automatically actuated apparatus, for a predetermined time period.

A combustible mixture may also be formed in the switch otherwise than by cir cuit interruption, as by the heat of the air surrounding the switch, or the heat of the current-carrying components.

A further object of this invention is to provide means to ventilate the switch and remove any combustible mixture or gases which may be formed in the switch.

'A further object is to effect the operation of the gas removing means during the period that the switch is in restraint against reclosing.

The gas removing means may comprise an ejector in communication with the expansion chamber of the switch. The ejector may be operated by a suitable fluid, as air, supplied by some source of high pressure, as an auwhen the tripping sociated with the valve to hold it open for a period of time sufficient to insure-the re moval of a combustible mixture within the switch and then close. A switch may be associated with said valve to control the closing circuit ofthe main switch and so arranged as to open and interrupt the closing circuit of the main switch when said valve is open, whereb to prevent the main switch from being rec osed, and to close when the valve closes to complete the closing circuit of the switch, and permit the main switch to be reclosed.

A further object of the invention is to providemanually controlled means by which thei gas removing means may be operated at wi l.

A further object of the invention is' generally to improve the construction and operation of electric circuitinterrupters.

A co-pending application of mine, Serial No. 561,756, filed ay 17, 1922, and one of \Villiam S. Edsall, Serial No. 546,713, filed March 25 1922, and a divisional application thereof Serial No. 692,874, filed February 14, 1924, all assigned to Sears B. Condit, disclose certain features of the invention.

The figure illustrates diagrammatically an electric circuit interrupter embodying my invention.

As here shown, the circuit interrupter comprises the oil switch 10 having the stationary switch members 11 and movable switch member 12 and the operating mechanism 13. The electric switch maybe closed by the closing coil 14 and openedby the opening or trippin C0ll 15. The switch may be controlled rom a remote point by means of the control switch 16 which, when moved into electrical engagement with the upper contact member 17 completes the closing circuit 18 including the battery 19 and closing coil 14 to close the switch. When said control switch 16 is moved to the lower contact member 20, it operates to complete the opening or tripping circuit 21 including the tripping coil 15, to effect the opening of the switch.

The switch 10 may control the circuit 25 and said circuit may have an overload relay 26 associated therewith and said relay may be arranged to bridge the contacts 27 upon an overload to complete the tripping circuit 21 and trip the switch open independently of the control switch 16. Said overload relay 26 may be of the instantaneous type or it may have a retardation device 28 associated therewith, as desired.

The switch and the control circuits above described are more or less common in the art.

The switch 10 is provided with a gas expansion space a above the oil therein. Due to circuit interruption or other causes, some of the oil, or other circuit interrupting me dium, may be converted into a vapor or gas and commingle with the air contained in the expansion space in the switch to form an explosive mixture. The mixture may not explode at the time it is formed but may explode upon the following circuit interruption and cause damage if permitted to remain in the switch. In accordance with my invention, I provide means to remove the gas and vapor that may collect in the expansion space of the switch after each opening movement of the switch and replace the gaseous contents of the switch with fresh air. The gas removing means may comprise the ejector 30. Said ejector may be in communication with the upper, or any desirable, part of the expansion space of the switch by the pipe 31, and may be supported by the casing through said i e. resh atmospheric air may be admltted into the switch through the pipe 32. Preferably said pipes 31 and 32 are oppositely disposed in the switch and one will be connected with the upper portion of the chamber while the other will be connected with the lower portion of the chamber whereby to expedite replacement of a combustible mixture within the switch by fresh air.

The ejector 30 may be of any suitable or desirable construction and may be provided with a discharge pipe 33 to convey the explosive mixture to any suitable location beyond the switch.

Said ejector 30 may be operated, either continually or intermittently, by a suitable source of high pressure fluid as, for instance, air may be supplied by the air compressor 35 which may be automatically operated to maintain a constant air pressure in the storage tank 36. An air pipe 37 may extend from said storage tank 36 to the ejector 30. The operation of said ejector 30 may be controlled manually by any suitable means or, and preferably, by means hereinafter to be described, or it may be automatically controlled. The controlling means for the ejector includes the valve 38 disposed in said high pressure airpipe 37. Said valve is arranged normally to be closed but, when opened, permits air at high pressure to pass into the ejector; and said ejector operates to remove or suck out the gaseous contents of the expansion space of the switch. The movable member, or valve stem, 39 of said valve may be controlled by the electro-magnetic device or solenoid 40 which is preferably included in the tripping circuit 21 of the switch. A dash pot 41 is associated with said valve stem 39 and the arrangement is such that when the solenoid 40 is energized, the valve may be moved rapidly into open position and the dash pot will delay the closing of the valve for a predetermined period whereby to provide time sufficient to ctiect the removal of any combustible mixture within the switch. lVith the arrangement above set forth, it will be noted that when the tripping circuit 21 is energized, either by the control switch 16 or by the overload relay 26, said solenoid 40 will be operated to open the air valve 38 and said air valve will remain open for a predetermined period of time subsequent the de-energization of the solenoid and then close.

The movable member 39, the solenoid 40 and the retardation device 41 are also arranged to control the reclosing of the switch and to prevent the reclosing of the switch until a sufficient period of time has elapsed to permit the ejector 30 to condition the switch for further operation at its normal capacity.

For this purpose, the movable member 39 of the air valve 38 is provided with the bridging member 42 which is arranged to bridge and electrically connect the contact members 43 included in the switch-closing circuit 18. The arrangement is such that under normal conditions and when the valve 38 is closed, said bridging member 42 will bridge and electrically connect the contact members 43 and thereby maintain the continuity of the closing circuit 18 at this oint whereby to permit the switch to be c osed through said control circuit. When the switch 10 is opened under load or otherwise, the solenoid 40 in the tripping circuit 21 of the switch is energized to open the valve 38 and actuate the ejector and also to move the bridging member 42 from the contacts 43 and break the closing circuit 18. The retardation device 41 maintains the bridging member 42 out of electrical engagement with the contact members 43 until a sufiicient period of time has lapsed to remove a combustible mixture from the switch and during this peiod, the switch can not be closed.

With this arrangement, the switch may always be in condition to interrupt the maxi- .num current for which it has been designed.

If desired, the control of the ejector 30 may be effectedmanually at a remote point.

A control circuit may include the solenoid 40, which latter may be controlled by the button 46. When the button 456 is depressed, the solenoid 40 is energized to open the valve 38 and eflt'ect the operation of the ejector. With this arrangement the retardation device 41 and the bridging member a2 may or may not be associated with the solenoid 40 and the valve 38 and the button 46 may be manually held depressed for a suflicient leiigth of time to enable the ejector to clear the switch and said button 46 may be disposed on the switch board adjacent the main switch. I

I claim:

1. An electric switch, and means rendered effective by the opening of the switch when it is open to ventilate the switch.

2. An electric switch having means to ventilate it automatically prior to successive openings thereof and when it is open.

3. An electric switch having means arranged automatically to ventilate it during its open condition.

4. An electric switch having a control circuit, and means governed by said control circuit arranged to exhaust the switch of its gaseous contents.

5. An electric switch having an opening circuit, and means controlled by said opening circuit arranged to ventilate the switch.

6. An electric switch having ventilating means for it, and remote controlling means for said ventilating means.

7. An electric switch having a remote controlling device for it, ventilating means for switch against closing for a predetermined period of time after it has opened, and means to ventilate the switch during such period.

10. An electric switch having a closing circuit, means governed by the opening of the switch to disable said closing circuitfor a predetermined period of time after the switch has opened, and means to ventilate the switch during such period.

11. An electric switch having a closing circuit, means governed by the opening of the switch to disable said closing circuit for a predetermined period of time after the switch has opened, and means governed by the aforesaid means to ventilate the switch.

12. An electric switch having closing and opening circuits, means governed by said opening circuit to disable said closing circuit for a predetermined period of time, and means governed by the aforesaid means to ventilate the switch during such period.

13. An electric switch having means to ventilate it and means to hold the switch in open position during the ventilation thereof.

name to this specification.

GEORGE A. BURNHAM. 

